Curable fluorinated elastomer compositions utilizing addition reaction between alkenyl and hydrosilyl groups are well known in the art. These compositions can be rendered self-adhesive by adding an organopolysiloxane having a hydrosilyl group and an epoxy and/or trialkoxysilyl group as the third component, as disclosed in JP 3239717 and JP 3567973. These compositions may cure on brief heating into elastomers having advantages including solvent resistance, oil resistance, chemical resistance, heat resistance, low-temperature properties, low moisture permeability, and electric insulation. They are used in the adhesive application in various industrial fields where such properties are required, and frequently for the bonding and sealing of electrical components in the automotive industry.
However, under rigorous conditions, for example, when exposed to a hot, strongly acidic atmosphere such as emissions from automotive gasoline and Diesel engines, or when contacted with or immersed in hot rancid deteriorated oils (e.g., engine oil and transmission oil), these cured elastomers shortly undergo discoloration or degradation, resulting in a substantial loss of sealing function. Even in the bonding and sealing application of electric and electronic components, there are increasing chances to encounter a rigorous environment. It would be desirable to have an adhesive composition which cures into a product having not only the above-listed properties, but also improved acid resistance.
It is noted that JP 2990646 discloses a polymer having a terminal structure [aromatic ring-Si-vinyl]. While this polymer is good in fast curing due to the inclusion of [Si-vinyl], the linkage between aromatic ring and Si is known to be acid labile. On the other hand, polymers free of [aromatic ring-Si-vinyl] at their terminus, for example, a polymer having a terminal structure [aromatic ring-alkylene-vinyl] and a polymer having a terminal structure [amide (having pendant aromatic ring substituent)-alkylene-vinyl] have good acid resistance, but are inferior in fast curing.
Citation List
    Patent Document 1: JP 3239717 (U.S. Pat. No. 5,656,711, EP 0765916)    Patent Document 2: JP 3567973 (U.S. Pat. No. 6,417,311, EP 1081185)    Patent Document 3: JP 2990646